In the processing of semiconductors for use in various electronic applications, it is frequently necessary to subject semiconductors to thermal processing or to coat them by such means as chemical vapor deposition. Semiconductors are typically furnished in the form of thin wafers which are treated in special furnaces or coating chambers. In order to prevent injury to the wafers, it has been found desirable to hold them in position during processing by means of slotted racks. The racks are typically placed in semi-open containers for ease in handling and to facilitate coating. One form of container which has been used is a cage boat which is a solid, two-part container provided with slots. The semiconductor wafers are placed within the cage boat, and the cage boat is then placed within the furnace or coating chamber. It is desirable to use a cylindrical configuration for the cage boat, in order to ensure uniformity in the processing of the semiconductor wafers.
In the past, racks for holding wafers of semiconducting materials and cage boats containing such racks have been fabricated of quartz. However, quartz cage boats must be handmade, requiring skilled labor and resulting in a relatively expensive device. In addition, quartz cage boats are characterized by poor dimensional tolerances. By their very nature, items fabricated from quartz are fragile. Quartz cage boats were therefore frequently broken during use. Another disadvantage of quartz cage boats is that cleaning with hydrofluoric acid, which is necessary to remove accumulations of silicon dioxide, results in the quartz being attacked by the acid and being devitrified, thereby reducing the strength of the cage boat, changing its dimensions and producing particles on the surface thereof which can contaminate the semiconductor wafers during processing.
Recently, cage boats have been produced from silicon carbide. Silicon carbide cage boats are stronger and more resistant to hydrofluoric acid than quartz, but they are expensive, difficult to fabricate and, in general, cannot be made with desired dimensional tolerances.
Because of the expense of fabricating cage boats and the need for frequent replacement thereof, it would be desirable to provide a cage boat constructed of easily fabricated material which could be readily disassembled for replacement of damaged parts.